In erecting an offshore platform, it is necessary to support a fixed platform with a number of legs. In one instance, the entire platform can be built on shore, complete with legs, towed to sea and thereafter positioned in an upright posture. A more popular method involves the procedure of positioning a pile jacket at a specified angle above the bottom and thereafter aligning a pile with the pile jacket. The pile is driven into the bottom by means of a pile driver. This method requires a barge to float the pile and jacket components to the site. It requires a separate barge equipped with a crane and a crane suspended pile driver. After the jacket is set in the ocean bottom, the barge supported crane is then maneuvered to lift a first segment of the pile which is threaded into the pile jacket. This is difficult because the pile jacket is ordinarily positioned at an angle with respect to the vertical. Moreover, the crane is supported by a barge which is moved by wave action. In view of the fact that the pile may weigh several tons and must be swung over at an angle to be snaked into the pile jacket, this procedure is difficult to implement. Indeed, occasions have occurred where hours have been required to thread the first pile segment into the pile jacket.
The apparatus of the present invention overcomes this severe problem. One feature of this invention is an apparatus comprised of a joined pile jacket and pile segment. They are joined together by means of connective links which can be selectively removed. They are joined together to travel as a unit with the pile segment received in the pile jacket. They are transferred by flotation or by barge. Moreover, the pile segment is located in the jacket from the beginning so that the most difficult step is avoided. This, therefore, enables the pile jacket to be positioned at an angle to guide the pile as it is erected on the ocean bottom without delay. Further, the releasable and connective links which join the two together are subsequently removed to enable the pile segment to be driven by a pile driver into the ocean bottom. Many pile segments can be joined together. In practical circumstances, it is not uncommon for a pile to be up to about 800.0 feet in length, typically with 400.0 feet of the pile driven into the ocean bottom and the remaining portions standing above the bottom to support a platform.
One advantage of this invention is the method of installation of a pile from segments on an ocean bottom. Another advantage of the method is the manner in which the pile segment and subsequently added segments are handled at the time of installation. The pile segment is secured by connective links on the interior of the pile jacket and at the end of the pile segment. Briefly, the connective links serve as anchors so that the two parts do not rattle or bang together during transit. Moreover, at the time of installation, they secure the pile segment at a location enabling an overhead crane to grab and manipulate the pile segment.
The connective links supporting the pile segment in the jacket include the feature of an elongate slot tolerating sliding movement. Sliding movement is tolerated so that the barge which supports the crane is free to bob up and down with wave action. Even though it may bob, it can still be used to handle the pile segment.
These features and many others are provided by the present invention which is summarized as a method and apparatus directed to a pile jacket and segmented pile arrangement. The apparatus utilizes an external pile jacket which surrounds a telescoped pile segment. The telescoped jacket and pile segment are thus handled as a unit from the time of manufacture until they are installed at an angle, typically by utilizing a derrick crane to set the pile jacket in the ocean bottom.
The procedure of the present invention thus contemplates the use of connective links to join the pile segments and pile jacket. The connective links are defeated when it becomes necessary to drive the pile segment into the ocean bottom. The pile segment is driven until it is substantially into the mud at which time it is necessary to attach other pile segments to extend the total length of the pile. The present apparatus includes connective links which assist in that also.